Meth user. Unable to get proper erection. What should I do?

Hi so I am a merch user and I inject it I he only shot up in my arms but recently web I get an erection it is painful and seems like the vein or tissue that's suppose to get filled wih blood is a hard lump

Meth or methamphetamine is a stimulant drug. It is used by youngsters as a drug of abuse to get euphoric effects. There are various subjective effects of meth on erection. It causes prolonged erection and delayed ejeculation. Due to prolonged erection and forceful sexual activity injury to blood vessels of penis occur. Injury result in leakage of blood and formation of microhematoma. The micro hematomas are felt like cord. Although you have reported that you have normal erection but usually on long term meth causes erectile dysfunction.
You have poor erection and lump on one side. I would advise you to refrain yourself from any sexual activity for at least 2 weeks, even try to avoid erection. Although morning erection will occur still try to avoid excitement. With time lump will get dissolved and you will be normal again.
Stop taking meth now, it is very harmful.
the one side of penis has developed microhematomas and this has resulted in decrease in the supply on that particular side. This is causing poor erection on that side. Wait for hematoma to resolved and if you are still under tension and having no improvement then I would advise you to get doppler study of penis done. It will delineate any deficits in blood supply to a particular area.
Hope I solved your question, if you have more questions you can ask again.